Stem strength plays a crucial role in the growth and development of plants, as well as in their flowering and fruiting. It not only impacts the lodging resistance of crops, but also influences the ornamental value of ornamental plants. Stem development is closely linked to stem strength; however, the roles of the SPL transcription factors in the stem development of herbaceous peony (Paeonia lactiflora Pall.) are not yet fully elucidated. In this study, we obtained and cloned the full-length sequence of PlSPL14, encoding 1085 amino acids. Quantitative real-time PCR (qRT-PCR) analysis revealed that the expression level of PlSPL14 gradually increased with the stem development of P. lactiflora and was significantly expressed in vascular bundles. Subsequently, utilizing the techniques of virus-induced gene silencing (VIGS) and heterologous overexpression in tobacco (Nicotiana tabacum L.), it was determined that PlSPL14-silenced P. lactiflora had a thinner xylem thickness, a decreased stem diameter, and weakened stem strength, while PlSPL14-overexpressing tobacco resulted in a thicker xylem thickness, an increased stem diameter, and enhanced stem strength. Further screening of the interacting proteins of PlSPL14 using a yeast two-hybrid (Y2H) assay revealed an interactive relationship between PlSPL14 and PlSLR1 protein, which acts as a negative regulator of gibberellin (GA). Additionally, the expression level of PlSLR1 gradually decreased during the stem development of P. lactiflora. The above results suggest that PlSPL14 may play a positive regulatory role in stem development and act in the xylem, making it a potential candidate gene for enhancing stem straightness in plants.

Seeds of Paeonia lactiflora Pall. ‘Hangshao’ contain over 20% oil, of which more than 90% are unsaturated fatty acids, showing its high potential as an oil crop. Triacylglycerol (TAG) is the main storage form of fatty acids, and diacylglycerol acyltransferase 2 (DGAT2) is a key enzyme in TAG biosynthesis. In this study, the full-length cDNA of PlDGAT2 (326 amino acids) was cloned. Subcellular localization assays further indicated that it localized in the endoplasmic reticulum. Functional verification showed that silencing PlDGAT2 in herbaceous peony decreased the level of total fatty acids, palmitic acid (C16:0, PA) and α-linolenic acid (C18:3, ALA), but increased linoleic acid (C18:2, LA) in leaves. Overexpressing PlDGAT2 in tobacco elevated the content of total fatty acids, PA, and ALA in seeds, while also enlarging the seed sizes, but it reduced the LA content in tobacco seeds. This study suggests that PlDGAT2 contributes to the accumulation of ALA and total fatty acids, offering a potential gene target for improving the oil quality of herbaceous peony seeds.